AU632589B2

AU632589B2 - Improved surface blackening treatment for zinciferous surfaces

Info

Publication number: AU632589B2
Application number: AU57839/90A
Authority: AU
Inventors: Hitoshi Ishii; Toshi Miyawaki; Kazuhiko Mori
Original assignee: Henkel Corp
Current assignee: Henkel Corp
Priority date: 1989-06-27
Filing date: 1990-06-26
Publication date: 1993-01-07
Anticipated expiration: 2010-06-26
Also published as: ZA904845B; AU5783990A; BR9003013A; EP0405340A1; CN1050572A; US5091223A; JPH0331484A; CA2019810A1

Description

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s 1 i x 632589 Form COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-69 COMPLETE SPECIFICATION

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Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: SPriority Related Art HENKEL CORPORTION, Name of Applicant 0 Address of Applicant Actual Inventor: Address for Service 300 Brookside Avenue, Ambler, United States of America.

Pennsylvania 19002.

KAZUHIKO MORI, TOSHI MIYAWAKI and HITOSHI ISHII.

WATERMARK PATENT TRADEMARK ATTORNEYS.

LOCKED BAG NO. 5, HAWTHORN, VICTORIA 3122, AUSTRALIA Complete Specification for the invention entitled: IMPROVED SURFACE BLACKENING TREATMENT FOR ZINCIFEROUS SURFACES Thu following statement is a full description of this invention, including the best method of performing it known to us L"8, la IMPROVED SURFACE BLACKENING TREATMENT FOR ZINCIFEROUS SURFACES Field of the Invention This invention relates to a treatment method for blackening surfaces consisting predominantly of zinc, including galvanized steel or other zinc coated base metal material, made by electrogalvanization, zinc-alloy electroplating, hot-dip galvanizing, and the like. The method finds use in optical instruments, solar-energy absorbing panels, and any other applications which require a black, corrosion-resistant coating on a object with a 7inciferous surface, one consisting predominantly of zinc. Unless the context requires otherwise, the term "zinc" here- .0 inafter shall be understood to include both pure zinc and zinc alloys that are predominantly zinc and to include surface coatings as well as solid objects with a surface the same as the interior.

Statement of Related Art Various methods are known for blackening zinc and galvanized material by chemical treatment. An example of this art is the blackening treatment method disclosed in Japanese Patent Application Laid Open (Kokai] "Tumber 61- 253381 [253,381/86]. This blackening treatment method employs an acidic aqueous solution, with a pH of 1.5 to 4, which contains an oxidizer, at least 1 gram per liter of Cu 2 ions, and 1 to 30 weight referred to the Cu ions, of Ni ions. This solution is applied at a liquid temperature of 20 to 70 degrees Centigrade 1 to seconds, and because of its acidity, requires a relatively expensive corrosion resistant treatment container.

The black film obtained by this treatment contains Cu and Ni in order to increase the weldability. The Cu, because it accelerates zinc corrosion by forming local galvanic cells with the underlying zinc, degrades the corrosion resistance and also reduces the adherence of the black surface film to the substrate.

It is an object of the present invention to provide a surface blackening treatment for zinc with improved corrosion resistance and adherence to zinc. It is another object of this invention to provide such a treatment from a less corrosive solution than that described immediately above for the same purpose.

Description of the Invention In this description, except in the working examples and the claims, or where expressly indicated to the contrary, all numbers specifying amounts of materials or conditions of reaction or use are to be understood as modified by the term "about". Also, it is to be understood that the SS4 presence of necessary counterions is implied for any constituint stated herein in ionic terms.

Oie embodiment of the present invention is a process for form[ng a blackened layer on a zinc surface by contacting the zinc surface with a treatment solution which has a pH of CU 2 s5 and which comprises, or preferably consists essentially of, water and: at least 0.5 g/L of the treatment solution of ions selected from the group consisting of Ni 2+ C 2+ and mixtures thereof; and an amount, sufficient to complex all the ions of -'a Sf component of a weak complexing component selected from the group consisting of aaaea, saturated aliphatic compounds having at least two amino groups of which at least one is a primary amino group, amino acids, and mixtures of any two or more of these; and, optionally but preferably, at least 50 parts per million by weight of a component selected from the group consisting of nitrite ions, nitrate ions, carbonate ions, thiocyanate ions, thiosuifate ions, thiourea, hypophosphite ions, phosphite ions, perchlorate ions, and mixtures of any two or more of these.

Ni 2 and/or Co 2 is preferably added to the treatment solution in the form of the sulfate or chloride. A Ni and Co precipitation sufficient to blacken the surface of zinc or galvanized material can be obtained at concentrations of at least 0.5 g/L for the total quantity of Ni 2 and/or 2+ Co 2 Furthermore, roughly the same effects are obtained 2+ 2+ even when the Ni and Co concentration is higher than this value.

2+ 2+ In addition to Ni and/or Co 2 another essential component of a treatment solution to be used according to this invention is made up of one or more compounds selected from ammonia, saturated aliphatic compounds having at least two hydrogen-containing amino groups, and amino acids.

Specific examples of the compounds having two amino groups of which at least one is a primary amino group are ethyl- 00 0 enediamine, trimethylenediamine, N-methylethylenediamine, N-ethylethylenediamine, N-n-propylethylenediamine, N,N-di- 30 methylethylenediamine, 1,2-diaminopropane, meso-2,3-diaminobutane, racemic-2,3-diaminobutane, cis-2,3-diaminocyclohexane, trans-l,2-diaminocyclohexane, trans-1, 2-diaminocycloheptane, diethylenetriamine, and triethylenetetramine.

Specific examples of suitable amino acids include alanine, glycine, aspartic acid, and glutamic acid. Any of these materials are added as complexing agents for the nickel I and/or cobalt present, and thus must be added in a quantity 4 at least stoichiometrically sufficient to complex all of the nickel and cobalt.

The treatment solution of the invention also preferably contains, as an additional component, at least 50 ppm of one or more ions or compounds selected from nitrite ions, nitrate ions, carbonate ions, thiocyanate ions, thiosulfate ions, thiourea, hypophosphite ions, phosphite ions, and perchlorate ions. These compounds, with the exception of thiourea, are usually added in the form of their alkali metal or ammonium salts. Thiourea is added as such. The advantage associated with the presence of these compounds is an acceleration of the tendency of zinc from the surface being treated to dissolve and thereby to accelerate precipitation onto the metal surface of nickel and/or cobalt from the complexes in which these metals are the central metal element. While this increased precipitation rate can be clearly observed after the addition of a total of at least 50 ppm (referred to the treatment solution) of one or more of the aforementioned additive compounds, an excellent precipitation enhancing effect S 15 is also obtained with higher concentrations than this. Accordingly, an optimum concentration may be selected based on economic considerations, balancing the higher cost for materials of a higher concentration against the savings in capital cost from faster operation of the process.

Preferably the process is performed in such a manner that from 80 to 200 milligrams per square meter ("mg/m 2 of the total of Ni and Co is precipitated on the treated surface during a contact time of preferably from 3 to 120 seconds at a temperature that is preferably between 20 and k0 1) G degrees Centigrade. Contact may be achieved by immersion, spraying, roll coating followed by passage through a squeeze roll, or any other suitable technique or mixture of techniques.

Alternatively, an electrolytic method, in which the treated surface of the workpiece is connected as a cathode to a source of electromotive force during immersion, can be used. In this case, the same quantity of Ni and/or Co as above can be deposited on the surface of the treated workpiece by carrying out electrolysis at a cathode current density of 1 to 100 amperes per square decimeter ("amp/dmn 2 for 2.0 to 10.0 seconds.

The practice of the invention may be further appreciated from the following, non-limiting, illustrative and comparison examples.

Examples General Conditions All the treatments in the examples and comparison examples were dipping treatments, and, the exception of Comparison Example 3, the treatment t _iperature was 40 degrees Centigrade. The treatment temperature in Comparison 2+ 2+ Example 3 was 30 degrees Centigrade. The Ni 2 and Co 2 were added in the form of their sulfates; ammonia was added S in the form of 28 aqueous ammonia; the other complcxing agents were added in the form of the 100 powder or liquid; and the nitrite ion and other anionic additives were S 8 added in the form of the sodium salts. Sulfuric acid or 0 sodium hydroxide was used to adjust the pH. Example 7 from Japanese Patent Application Laid Open Number 61-253381 is reported herein as Comparison Example 3.

The evaluations were carried out as follows. The blackness was evaluated based on the L-value (fractional values were rounded to the decimal point) as determined using an SM color coyputer from Suga Test Instruments Company, Limited. The adherence was evaluated by folding once (usually designated in the art as and then peeling Swith transparent adhesive tape, and was scored using the ~v/N~ ii.l i following evaluation standards: no peeling; less than 10 peeling; A= 10 to less than 30 peeling; and x more than 30 peeling.

The specific treatment conditions and performance evaluations for Examples 1 through 9 and Comparison Examples 1 4 are reported in Table 1.

Discussion of the Evaluation Results The lower limit for the nickel and/or cobalt concentration is illustrated by a comparison of Example 4 (Co at 0.7 g/L) and Comparison Example 1 (Co at 0.3 While Comparison Example 1 has an unsatisfactory L-value of SExample 4 has a SaLisfulaory blackim.n wiLlh aL-vilu thus supporting a low er- .5 g/L for the tota~tonof nickel and cobalt n tr .tment-- -afaaw- The lower limit on the additive concentration is illustrated by a comparison among Examples 1 through 3.

Here, Example 2 (additive concentration 0.03 g/L) has the same blackness as Example 1 (no additive), while the blackness is clearly increased in Example 3 (additive concentration 0.07 This supports a value of 50 ppm 0.05 g/L) for the preferred lower limit for the additive concentration.

With regard to the treatment time, the L-value in Comparison Example 2 (2 second treatment) exceeds 20, which should be compared with Example 8 (5 second treatment).

This supports a preferred lower limit on the treatment time Sof 3 seconds.

SAn L-value of 12 was obtained in Comparison Example 3 through blackening with a precipitate other than nickel and cobalt, using a copper containing solution as described in Japanese Patent Application Laid Open Number 61-253382).

However, in this case the adherence was poor, so that substantial peeling with transparent adhesive tape was obtained after a 1T fold.

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1 Table 1. Examples (Treatment Conditions and Pr-perties) umnai type of retal added complexing ageot additive treatment pH L adherence plated time value steel sheet type g/L type g/L type g/L (seconds) EG N .0 lenediamine 30 20 7.5 18 Example EG Ni 5.0 ethylenediamine 130 SCN- 0.03 20 7.5 18 Example 2 EG N i 5.0 ethylenediamine .~30 SCN- 0.03 20 7.5 18 +4- EG N;ri .15.0 ethyeeimine 30 SCN 0.07 20 7.5 16 E--nl 01 N02o~1 Example L+ Zn-Ni Ni 2.0 diethylenetriamine 7 21P1'02- 1.0 40 7.0 14 Co 2.0 alanae 2 SC(NH 2 2 Example 5 Zn-Ni Ni 5.0 triethylenetetramine 10 C104- 2.0 30 6.5 15 I aspartic acid 2 P0 3 3 Example EG C 6.0 trimethylenediamine 10 N0 3 1.0 30 8.0 16 glutamic acid 2 C032- Example 7 Zn-Ni Ni 3.0 ammonia 10 20 5.5 18 4+ glycine Example EG Ni 10 ammonia 30 N02- 2.0 5 10.0 16 I N-methylethylencdiamine 5 S203 2 Comparison GI Co 0.3 ammonia 5 N02- 1.0 60 9.I 25 Example 1 Comparison EG Ni 10 ammonia 30 NO2- 2.0 2 10.0 22 4+ Example 2 N-methylethylenedaamine 5 S203 2 Comparison EG Ch 10 potassium 20 2 3.0 12 x Example 3 Ni 5.0 chlorate Comparison EG Ni 2.0 sodium glycortate 5 20 11.5 35 Exa ple4 I I

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20 g/m 2 electrogalvanization 20 -/m2 zinc-nickel alloy electroplating 90 S/m 2 melt galvanization l rx~,i-nr- 8 Benefits of the Invention The present invention achieves an excellent corrosion resistance and adherence through the use of a one-step treatment solution with pH 5, and is highly advantageous in terms of bath management, operations, and cost. In particular, there are fewer restrictions on the treatment container since the treatment solution has a pH of at least Another benefit of the present invention is that the rate of blackening can be readily increased by the addition of a displacement ligand (nitrite ion, nitrate ion, carbonate ion, and the like) to the treatment solution; this allows a reduction in treatment time and temperature.

What is claimed is:

Claims

1. A process for treating an object with a zinciferous surface, said process comprising a step of contacting the surface of the object to be treated with an aqueous liquid solution composition that has a pH of 5 to 10 and comprises water and the following components: at least 0.5 g/L of the treatment solution of ions selected from the group consisting of Ni2+, Co2+, and mixtures thereof; and an amount, stoichiometrically sufficient to complex all the ions of component of a weak complexing component selected from the group consisting of saturated aliphatic compounds having at least two amino groups of which at least one is a primary amino group, amino acids, and mixtures of any two or more of these.

2. A process as claimed in claim 1, wherein the solution additionally contains ammonia.

3, A process according to claim 1 or 2, wherein said aqueous solution composition additionally comphtes: at least 50 parts per million by weight, referred to the total solution composition, of a component selected from the group consisting of nitrite ions, nitrate ions, carbonate ions, thiocyanate ions, thiosulfate ions, thiourea, hypophosphite ions, phosphite ions, perchlorate ions, and mixtures of any two or more of these.

4. A process according to any one of the preceding claims, wherein a total amount of nickel and cobalt within the range from 80 to 200 mg/m2 of the zinciferous surface contacted is deposited on the surface during the process.

A process according to any one of the preceding claims, wherein the time of contacting between said zinciferous surface and said aqueous solution composition is between 3 and 120 seconds. ,1

6. A process according to any one of the preceding claims, wherein the temperature during contacting between said zinciferous surface and said aqueous solution composition is between 20 and 80 degrees Centigrade.

7. A process according to any one of the preceding claims, wherein the contacting is accomplished by immersion, spraying, or roll coating. DATED THIS 26TH DAY OF OCTOBER, 1992 HENKEL CORPORATION WATERMARK PATENT TRADEMARK ATTORNEYS THE ATRIUM 290 BURWOOD ROAD S HAWTHORN VICTORIA 3122 .AUSTRALIA DBM:JC DOC 23: AU5783990.WPC N 44, to